THE EFFECT OF LIGHT QUALITY ON THE PRODUCTS OF PHOTOSYNTHESIS IN CHLORELLA VULGARIS

Abstract

Suspensions of Chlorella vulgaris, grown in synchronous culture, were pretreated in darkness for 45 to 225 minutes and illuminated in the presence of C14-bicarbonate with red, with red plus 4% of blue, and with blue light alone. The light intensities were so adjusted that the rate of photosynthesis (fixation of C14) was the same under the different conditions of illumination. The distribution of C14 among the various compounds of the ethanol-soluble fraction was obtained using paper chromatography and autoradiography.After 5 minutes of photosynthesis, the incorporation of C14 into aspartic acid was higher in the presence of red with supplementary blue light than in red light alone. At the same time the total radioactivity in glycine plus serine and in glycolic acid decreased. After 30 minutes of photosynthesis, blue light supplementary to red and blue light alone increased the total incorporation of C14 into the amino acid plus organic acid fraction as compared with incorporation in red light. This was due mainly to an increase in the radioactivity of aspartic and glutamic acids, while at the same time the radioactivity in glycine and glycolic acid was reduced.The duration of dark pretreatment was an important factor in the 30-minute experiments. The effect of increased dark pretreatment was to lower the incorporation of C14 into aspartic and glutamic acids when photosynthesis was carried out in red light, but the incorporation of C14 into these acids was increased in the presence of supplementary blue light.It is concluded that the distribution of carbon among the products of photosynthesis is affected by the quality of light.